Jithin S Kumar, Abhijit Chaudhuri, Ramesh Kannan Kandasami
Subsurface exploration typically requires application of cycles of fluid pressures on the surface of the cylindrical cavity during wellbore circulation. In this study, a numerical model is proposed that can capture the evolution of the elastic‐plastic boundary and the shear‐induced porosity/ stiffness changes during the cycles of cavity contraction and expansion. The developed solver is benchmarked against the existing experimental data and other numerical solutions. During pressure‐induced unloading and reloading of the cavity, increments are chosen so that the model satisfies the equilibrium conditions. When the stress state is reduced from the in situ stress to zero stress at the cavity boundary and then reloaded to a load ratio, it is observed that the material exhibits a stiffer, apparent elastic‐dominated response at higher load ratios. Additionally, when the porosity is updated for each material point, the maximum radial displacement during unloading increases by nearly 20%, and the recovered stress after reloading decreases by approximately 15% compared to the case of constant porosity. Parametric studies on dimensionless factors further reveal that higher (effect of shear modulus) and (effect of pre‐consolidation pressure) values lead to narrower hysteresis loops, indicating that the medium reaches an elastic‐dominated response more rapidly. Quantitatively, increasing from 25.82 to 60.26 (with ) reduces the final specific energy by nearly 70%, while increasing from 1.25 to 2.00 (with ) results in a 30% reduction in energy dissipation.
{"title":"Geomechanical Unload‐Reload Response of Cylindrical Cavities for Wellbore Stability","authors":"Jithin S Kumar, Abhijit Chaudhuri, Ramesh Kannan Kandasami","doi":"10.1002/nag.70238","DOIUrl":"https://doi.org/10.1002/nag.70238","url":null,"abstract":"Subsurface exploration typically requires application of cycles of fluid pressures on the surface of the cylindrical cavity during wellbore circulation. In this study, a numerical model is proposed that can capture the evolution of the elastic‐plastic boundary and the shear‐induced porosity/ stiffness changes during the cycles of cavity contraction and expansion. The developed solver is benchmarked against the existing experimental data and other numerical solutions. During pressure‐induced unloading and reloading of the cavity, increments are chosen so that the model satisfies the equilibrium conditions. When the stress state is reduced from the in situ stress to zero stress at the cavity boundary and then reloaded to a load ratio, it is observed that the material exhibits a stiffer, apparent elastic‐dominated response at higher load ratios. Additionally, when the porosity is updated for each material point, the maximum radial displacement during unloading increases by nearly 20%, and the recovered stress after reloading decreases by approximately 15% compared to the case of constant porosity. Parametric studies on dimensionless factors further reveal that higher (effect of shear modulus) and (effect of pre‐consolidation pressure) values lead to narrower hysteresis loops, indicating that the medium reaches an elastic‐dominated response more rapidly. Quantitatively, increasing from 25.82 to 60.26 (with ) reduces the final specific energy by nearly 70%, while increasing from 1.25 to 2.00 (with ) results in a 30% reduction in energy dissipation.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"4 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145993114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a three‐dimensional (3D) analytical solution for deformation and stress changes inside and outside a geothermal reservoir that is under a prescribed temperature change, derived based on the Hankel transform and thermoelastic constitutive equations. The geothermal reservoir is bounded between two isothermal layers, with different mechanical moduli considered. Unlike most existing analytical models that are restricted to one‐dimensional (1D) or two‐dimensional (2D) frameworks, assume homogeneous rock properties, or ignore interlayer stiffness differences, the proposed solution innovatively captures 3D thermoelastic responses, explicitly accounts for distinct mechanical moduli between the reservoir and bounding isothermal layers, and integrates boundary effects. The solution is based on Navier's static equilibrium equations and derived under the boundary conditions of stress and deformation continuity at the interfaces between rock layers. Considering a uniform temperature change within the geothermal reservoir, this study analyzes the influence patterns of key parameters, including the thickness‐to‐diameter ratio of the temperature‐varying volume, the stiffness ratio of rock layers on reservoir compaction and stress changes inside and outside the reservoir. The magnitude and orientation variations of principal stresses around the geothermal reservoir are presented. Studies indicate that subsurface heterogeneity and the thickness‐to‐diameter ratio of the temperature‐varying volume have significant effects on stress redistribution, reorientation, and reservoir compaction. Additionally, results also reveal the influence of boundary effects on reservoir compaction. Practically, this 3D analytical solution is able to serve as a quantitative tool to assist in estimating reservoir compaction magnitude and understanding stress reorientation patterns, providing a reference for evidence‐based decisions in geothermal reservoir management.
{"title":"How Heat Extraction Reshapes Subsurface Stresses: A Three‐Dimensional Analytical Study of Layered Geothermal Reservoirs","authors":"Chengyu Yang, Diyuan Li, Fenghua Nie, Xing Su","doi":"10.1002/nag.70236","DOIUrl":"https://doi.org/10.1002/nag.70236","url":null,"abstract":"This paper presents a three‐dimensional (3D) analytical solution for deformation and stress changes inside and outside a geothermal reservoir that is under a prescribed temperature change, derived based on the Hankel transform and thermoelastic constitutive equations. The geothermal reservoir is bounded between two isothermal layers, with different mechanical moduli considered. Unlike most existing analytical models that are restricted to one‐dimensional (1D) or two‐dimensional (2D) frameworks, assume homogeneous rock properties, or ignore interlayer stiffness differences, the proposed solution innovatively captures 3D thermoelastic responses, explicitly accounts for distinct mechanical moduli between the reservoir and bounding isothermal layers, and integrates boundary effects. The solution is based on Navier's static equilibrium equations and derived under the boundary conditions of stress and deformation continuity at the interfaces between rock layers. Considering a uniform temperature change within the geothermal reservoir, this study analyzes the influence patterns of key parameters, including the thickness‐to‐diameter ratio of the temperature‐varying volume, the stiffness ratio of rock layers on reservoir compaction and stress changes inside and outside the reservoir. The magnitude and orientation variations of principal stresses around the geothermal reservoir are presented. Studies indicate that subsurface heterogeneity and the thickness‐to‐diameter ratio of the temperature‐varying volume have significant effects on stress redistribution, reorientation, and reservoir compaction. Additionally, results also reveal the influence of boundary effects on reservoir compaction. Practically, this 3D analytical solution is able to serve as a quantitative tool to assist in estimating reservoir compaction magnitude and understanding stress reorientation patterns, providing a reference for evidence‐based decisions in geothermal reservoir management.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"31 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145968581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The presence of a tension crack at the slope crest indicates a reduction in slope stability, particularly under seismic conditions. Therefore, the seismic stability of slopes with cracks requires special attention. In this study, the seismic stability of cracked rock slopes governed by the Hoek–Brown criterion is investigated within the framework of the kinematic approach of limit analysis. The strength nonlinearity of rock masses is represented by two stress variables on the slip surface using the pointwise equivalence strategy, instead of the single‐ or multi‐tangent technique. Seismic acceleration is incorporated through the classical pseudo‐static method. A discretization‐based approach is applied to construct the failure mechanism following the associative flow rule. The critical depth of a vertical crack under seismic loading is re‐derived and used as a boundary condition for the subsequent optimization. Closed‐form solutions for the stability number and the yield seismic coefficient are then obtained from the energy balance equation. Stability charts are presented for different seismic coefficients and combinations of rock strength parameters. The influence of slope inclination and rock strength on the yield seismic coefficient is also examined. Finally, two well‐recorded seismic waves are employed to estimate seismic permanent displacements using Newmark's method.
{"title":"Stability Assessment of a Rock Slope With Tension Cracks Subjected to Earthquakes","authors":"Zhengwei Li, Wenping Gong, Junhao Zhong","doi":"10.1002/nag.70232","DOIUrl":"https://doi.org/10.1002/nag.70232","url":null,"abstract":"The presence of a tension crack at the slope crest indicates a reduction in slope stability, particularly under seismic conditions. Therefore, the seismic stability of slopes with cracks requires special attention. In this study, the seismic stability of cracked rock slopes governed by the Hoek–Brown criterion is investigated within the framework of the kinematic approach of limit analysis. The strength nonlinearity of rock masses is represented by two stress variables on the slip surface using the pointwise equivalence strategy, instead of the single‐ or multi‐tangent technique. Seismic acceleration is incorporated through the classical pseudo‐static method. A discretization‐based approach is applied to construct the failure mechanism following the associative flow rule. The critical depth of a vertical crack under seismic loading is re‐derived and used as a boundary condition for the subsequent optimization. Closed‐form solutions for the stability number and the yield seismic coefficient are then obtained from the energy balance equation. Stability charts are presented for different seismic coefficients and combinations of rock strength parameters. The influence of slope inclination and rock strength on the yield seismic coefficient is also examined. Finally, two well‐recorded seismic waves are employed to estimate seismic permanent displacements using Newmark's method.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"51 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145968582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The horizontal force transmission mechanism of a cushion in a composite foundation is crucial in engineering practice, but has not been investigated systematically. An interface shear test and coupled discrete element method–finite difference method (DEM–FDM) were used to establish a rigid pile composite foundation model. The microscopic response of the cushion was analyzed by discrete element modeling to understand the microscopic force transmission mechanism of the cushion during the horizontal loading of the rigid pile composite foundation. The results showed that the stress field, coordination number field, and contact force chain reflected the internal force of the cushion under a horizontal load. The cushion layer exhibited a stress concentration as the horizontal load increased. The direction of the principal stress was deflected, and the direction of the force transmission changed from the vertical direction at the end of vertical loading to the direction of 45° due to the shearing action. The number of particle contacts in the area of the major principal stress increased, forming stronger contact force chains, and the coordination number of the soil particles increased.
{"title":"Microscopic Mechanism of Horizontal Force Transmission of a Cushion in a Rigid Pile Composite Foundation","authors":"Chenyu Lv, Yonghui Li, Yuancheng Guo, Hengyu Niu","doi":"10.1002/nag.70139","DOIUrl":"https://doi.org/10.1002/nag.70139","url":null,"abstract":"The horizontal force transmission mechanism of a cushion in a composite foundation is crucial in engineering practice, but has not been investigated systematically. An interface shear test and coupled discrete element method–finite difference method (DEM–FDM) were used to establish a rigid pile composite foundation model. The microscopic response of the cushion was analyzed by discrete element modeling to understand the microscopic force transmission mechanism of the cushion during the horizontal loading of the rigid pile composite foundation. The results showed that the stress field, coordination number field, and contact force chain reflected the internal force of the cushion under a horizontal load. The cushion layer exhibited a stress concentration as the horizontal load increased. The direction of the principal stress was deflected, and the direction of the force transmission changed from the vertical direction at the end of vertical loading to the direction of 45° due to the shearing action. The number of particle contacts in the area of the major principal stress increased, forming stronger contact force chains, and the coordination number of the soil particles increased.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"218 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145962066","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Based on the Hagen–Poiseuille law, a general imperfect flow contact model for a two‐layer soil system was constructed. In this model, the upper and lower layers are unsaturated and saturated soil, respectively. The laminar flow behavior, stemming from the low‐velocity flow of pore water along complex pore channels at the interface, was characterized by introducing the flow contact transfer coefficient () and flow partition coefficient (). The mechanical behaviors of unsaturated and saturated soils were described by Fredlund's unsaturated soil consolidation model and Terzaghi's saturated soil consolidation model, respectively. The semianalytical solution for the consolidation of unsaturated–saturated soil foundations was derived. This was achieved by applying the Laplace transform and the Crump inverse transform. The rationality of the model was validated through a comparative analysis of existing solutions. The research shows that the interface flow resistance effect significantly alters the distribution of pore water pressure. In the models considering interface flow resistance, relative pore water pressure gradients occur at interfaces. The gradient of pore water pressure at the interface in the general imperfect flow contact model is the most significant one among them. Moreover, the interface flow resistance effect reduces the settlement rate of the soil. Especially in the middle and later stages of settlement, the increase in the or the decrease in the has a more significant influence on the settlement in the process. Nevertheless, the final settlement amount is not influenced.
{"title":"Semianalytical Solution for One‐Dimensional Consolidation of Unsaturated–Saturated Soil Foundations Based on the Interfacial Flow Contact Resistance Model","authors":"Dansheng Yu, Minjie Wen, Xiaonan Ge, Yiming Zhang, Ji Wan, Shihan Lou","doi":"10.1002/nag.70237","DOIUrl":"https://doi.org/10.1002/nag.70237","url":null,"abstract":"Based on the Hagen–Poiseuille law, a general imperfect flow contact model for a two‐layer soil system was constructed. In this model, the upper and lower layers are unsaturated and saturated soil, respectively. The laminar flow behavior, stemming from the low‐velocity flow of pore water along complex pore channels at the interface, was characterized by introducing the flow contact transfer coefficient () and flow partition coefficient (). The mechanical behaviors of unsaturated and saturated soils were described by Fredlund's unsaturated soil consolidation model and Terzaghi's saturated soil consolidation model, respectively. The semianalytical solution for the consolidation of unsaturated–saturated soil foundations was derived. This was achieved by applying the Laplace transform and the Crump inverse transform. The rationality of the model was validated through a comparative analysis of existing solutions. The research shows that the interface flow resistance effect significantly alters the distribution of pore water pressure. In the models considering interface flow resistance, relative pore water pressure gradients occur at interfaces. The gradient of pore water pressure at the interface in the general imperfect flow contact model is the most significant one among them. Moreover, the interface flow resistance effect reduces the settlement rate of the soil. Especially in the middle and later stages of settlement, the increase in the or the decrease in the has a more significant influence on the settlement in the process. Nevertheless, the final settlement amount is not influenced.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"39 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145968580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kuangqin Xie, Zonghao Yuan, Yuwang Liang, Yuanqiang Cai
Inspired by the study of attenuation zone in periodic structures within solid‐state physics, periodic configurations have been increasingly utilized for vibration mitigation in rail transit systems. In this work, a semi–analytical solution is proposed to evaluate the vibration mitigation performance of periodic tubular barriers under underground moving train in a half‐space. The proposed solution is based on the wave function method, simultaneously considering the dynamic wheel‐rail coupling and multiple scattering effects among multiple embedded structures (tunnel and barriers). The multiple scattering interfaces involve the translation and transformation of wave functions. This developed method enables the assessment of vibration mitigation performance of periodic tubular barriers under underground moving trains. Furthermore, this study investigates the effects of spacing, material properties, and arrangement of the periodic tubular barriers. Numerical results demonstrate that the periodic configuration significantly mitigates train‐induced ground vibrations by broadening the attenuation bandwidth and improving reduction performance. Optimal performance is achieved when the shear wave bandgap overlaps the train's dominant vibration frequency.
{"title":"Semi‐Analytical Modeling of Periodic Tubular Barriers for Vibration Mitigation Under Underground Train","authors":"Kuangqin Xie, Zonghao Yuan, Yuwang Liang, Yuanqiang Cai","doi":"10.1002/nag.70234","DOIUrl":"https://doi.org/10.1002/nag.70234","url":null,"abstract":"Inspired by the study of attenuation zone in periodic structures within solid‐state physics, periodic configurations have been increasingly utilized for vibration mitigation in rail transit systems. In this work, a semi–analytical solution is proposed to evaluate the vibration mitigation performance of periodic tubular barriers under underground moving train in a half‐space. The proposed solution is based on the wave function method, simultaneously considering the dynamic wheel‐rail coupling and multiple scattering effects among multiple embedded structures (tunnel and barriers). The multiple scattering interfaces involve the translation and transformation of wave functions. This developed method enables the assessment of vibration mitigation performance of periodic tubular barriers under underground moving trains. Furthermore, this study investigates the effects of spacing, material properties, and arrangement of the periodic tubular barriers. Numerical results demonstrate that the periodic configuration significantly mitigates train‐induced ground vibrations by broadening the attenuation bandwidth and improving reduction performance. Optimal performance is achieved when the shear wave bandgap overlaps the train's dominant vibration frequency.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"8 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145968644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chenglin Wang, Jun Hu, Junzhi Sun, Famu Huang, Luokun Xiao, Quanrong Wang, Jianwei Bu
Depth‐decaying hydraulic conductivity () broadly exist in aquifers due to the increasing vertical geostatic stress, while it was generally estimated by the Uniform‐ model. In this study, a novel semi‐analytical model of pumping tests with depth‐decaying was developed using the Laplace transform method, Goldstein‐Weber transform method, and the Green's function method. The decay of along the depth profile was described using an exponential function. The new model was named the Decay‐ model, and it was tested by the finite‐difference solution and field data. Results indicated that the attenuation coefficient () had a significant impact on drawdown, and greater values resulted in greater drawdown rates. Although the Uniform‐ model performed well when fitting to the observation data at any one of the spatial locations in the heterogeneous aquifer, the estimated parameters cannot represent the real aquifer with decaying . The determination of aquifer heterogeneity required two or more sets of time‐serials drawdown at different aquifer locations with the distance between them as far as possible. The drawdown was more sensitive to the parameters of and the hydraulic conductivity at aquifer top than the other parameters. The Decay‐ model was an extension of the Uniform‐ model, and it outperformed in the interpretation of field pumping tests. The Decay‐ model is recommended, regardless of homogeneous or heterogeneous aquifers.
{"title":"A Novel Semi‐Analytical Model of Pumping Test With Depth‐Decaying Hydraulic Conductivity","authors":"Chenglin Wang, Jun Hu, Junzhi Sun, Famu Huang, Luokun Xiao, Quanrong Wang, Jianwei Bu","doi":"10.1002/nag.70233","DOIUrl":"https://doi.org/10.1002/nag.70233","url":null,"abstract":"Depth‐decaying hydraulic conductivity () broadly exist in aquifers due to the increasing vertical geostatic stress, while it was generally estimated by the Uniform‐ model. In this study, a novel semi‐analytical model of pumping tests with depth‐decaying was developed using the Laplace transform method, Goldstein‐Weber transform method, and the Green's function method. The decay of along the depth profile was described using an exponential function. The new model was named the Decay‐ model, and it was tested by the finite‐difference solution and field data. Results indicated that the attenuation coefficient () had a significant impact on drawdown, and greater values resulted in greater drawdown rates. Although the Uniform‐ model performed well when fitting to the observation data at any one of the spatial locations in the heterogeneous aquifer, the estimated parameters cannot represent the real aquifer with decaying . The determination of aquifer heterogeneity required two or more sets of time‐serials drawdown at different aquifer locations with the distance between them as far as possible. The drawdown was more sensitive to the parameters of and the hydraulic conductivity at aquifer top than the other parameters. The Decay‐ model was an extension of the Uniform‐ model, and it outperformed in the interpretation of field pumping tests. The Decay‐ model is recommended, regardless of homogeneous or heterogeneous aquifers.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"266 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145968579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rui‐Xiao Zhang, Xiang‐Sheng Chen, Dong Su, De‐Jin Zhang
Gravity‐driven granular flows are a fundamental geological hazard. Among the various dynamic aspects of granular flow that are still being explored, the consideration of the bedding angle stands out as particularly significant. In this study, granular columns with different bedding angle and varying aspect ratios ( AR s) (initial height/initial length) were examined by discrete element method simulations. The results showed that the entire collapse process can be categorized into three distinct stages: initiation, collapse, and accumulation. The runout distance of the granular column with a larger bedding angle extends farther at the same time point. Two distinct final deposit profiles were identified with reduced trapezoidal and triangular shapes. A comparison of the absolute values of the maximum differential sedimentation angles shows a clear increase with the bedding angle. The highest value of maximum kinetic energy consistently occurs in the model with a bedding angle of 90° across all aspect ratios. The maximum dissipated energy increases as AR increases. The bedding angle significantly influences the extent of coordination number (CN) reduction, with larger bedding angles resulting in a more pronounced decrease in CN. As the bedding angle increases, the degree of anisotropy in the particle system intensifies. As the granular column collapses, the degree of anisotropy gradually diminishes. Increasing the aspect ratio significantly amplifies the degree of anisotropy.
{"title":"Impact of Bedding Angle on the Processes of Granular Column Collapse","authors":"Rui‐Xiao Zhang, Xiang‐Sheng Chen, Dong Su, De‐Jin Zhang","doi":"10.1002/nag.70224","DOIUrl":"https://doi.org/10.1002/nag.70224","url":null,"abstract":"Gravity‐driven granular flows are a fundamental geological hazard. Among the various dynamic aspects of granular flow that are still being explored, the consideration of the bedding angle stands out as particularly significant. In this study, granular columns with different bedding angle and varying aspect ratios ( <jats:italic>AR</jats:italic> s) (initial height/initial length) were examined by discrete element method simulations. The results showed that the entire collapse process can be categorized into three distinct stages: initiation, collapse, and accumulation. The runout distance of the granular column with a larger bedding angle extends farther at the same time point. Two distinct final deposit profiles were identified with reduced trapezoidal and triangular shapes. A comparison of the absolute values of the maximum differential sedimentation angles shows a clear increase with the bedding angle. The highest value of maximum kinetic energy consistently occurs in the model with a bedding angle of 90° across all aspect ratios. The maximum dissipated energy increases as <jats:italic>AR</jats:italic> increases. The bedding angle significantly influences the extent of coordination number (CN) reduction, with larger bedding angles resulting in a more pronounced decrease in CN. As the bedding angle increases, the degree of anisotropy in the particle system intensifies. As the granular column collapses, the degree of anisotropy gradually diminishes. Increasing the aspect ratio significantly amplifies the degree of anisotropy.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"47 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145937987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaolin Huang, Weiqi Kang, Cong Yin, Tiangang Lan, Jiahu Du
Rocks exhibit nonlinear and hysteretic deformation during loading–unloading cycles, with elastic modulus and plastic strain evolving with increasing cycle numbers and thereby affecting microcracking patterns and acoustic emission (AE). These processes are governed by micromechanical responses of heterogeneous microstructures, yet existing models often fail to represent them accurately. To address this gap, we developed a nonlinear bonded particle model (NBPM) within the discrete element method, incorporating microstructural hardening and memory effects. Compared with conventional linear bonded particle model (LBPM), the NBPM more reliably reproduces the hysteresis response of sandstone under variable‐amplitude cyclic compression, particularly elastic modulus strengthening and cumulative plastic deformation. Model analyses show that compression hardening and memory effects at mineral grain contacts amplify microstructural heterogeneity, producing incompatible deformation and tensile stress concentration zones. During unloading, the abrupt increase in contact stiffness raises the number of tensile stress concentration zones, which expand with increasing cycle numbers. Cyclic compression primarily induces tensile microcracks parallel to the loading direction, whereas unloading significantly enhances the formation of perpendicular tensile cracks. The growth rate of microcracks accelerates as the cycle numbers increase. AE results reveal a stepwise increase in events and energy release, starting with gradual growth and followed by rapid acceleration. Initial unloading is dominated by low‐energy tensile fractures, while amplified cyclic loading produces more high‐energy fracture events. The b ‐value shows a consistent decline with increasing cycle number. This study provides a mechanistic framework linking microstructural hardening, memory effects, and AE evolution, offering new insights into the multi‐scale mechanical response of rocks under cyclic disturbances.
{"title":"DEM Modeling of Microcracking and Acoustic Emission in Rock under Cyclic Compression with Microstructural Hardening and Memory Effects","authors":"Xiaolin Huang, Weiqi Kang, Cong Yin, Tiangang Lan, Jiahu Du","doi":"10.1002/nag.70226","DOIUrl":"https://doi.org/10.1002/nag.70226","url":null,"abstract":"Rocks exhibit nonlinear and hysteretic deformation during loading–unloading cycles, with elastic modulus and plastic strain evolving with increasing cycle numbers and thereby affecting microcracking patterns and acoustic emission (AE). These processes are governed by micromechanical responses of heterogeneous microstructures, yet existing models often fail to represent them accurately. To address this gap, we developed a nonlinear bonded particle model (NBPM) within the discrete element method, incorporating microstructural hardening and memory effects. Compared with conventional linear bonded particle model (LBPM), the NBPM more reliably reproduces the hysteresis response of sandstone under variable‐amplitude cyclic compression, particularly elastic modulus strengthening and cumulative plastic deformation. Model analyses show that compression hardening and memory effects at mineral grain contacts amplify microstructural heterogeneity, producing incompatible deformation and tensile stress concentration zones. During unloading, the abrupt increase in contact stiffness raises the number of tensile stress concentration zones, which expand with increasing cycle numbers. Cyclic compression primarily induces tensile microcracks parallel to the loading direction, whereas unloading significantly enhances the formation of perpendicular tensile cracks. The growth rate of microcracks accelerates as the cycle numbers increase. AE results reveal a stepwise increase in events and energy release, starting with gradual growth and followed by rapid acceleration. Initial unloading is dominated by low‐energy tensile fractures, while amplified cyclic loading produces more high‐energy fracture events. The <jats:italic>b</jats:italic> ‐value shows a consistent decline with increasing cycle number. This study provides a mechanistic framework linking microstructural hardening, memory effects, and AE evolution, offering new insights into the multi‐scale mechanical response of rocks under cyclic disturbances.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"29 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145937988","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A viscoelastic solution for layered porous media subjected to nonlinear Stokes waves is developed based on fully dynamic poroelastic theory and Stokes wave theory. Specifically, a unified expression for the wave‐induced dynamic pressure is constructed by Euler's formula in a complex exponential form, enabling the extension from linear to nonlinear wave expressions. The complex modulus of the medium is obtained by applying properties of the Gamma function to the fractional standard linear solid model. By invoking the elastic‐viscoelastic correspondence principle, the elastic solution is further extended to viscoelasticity. Then, the governing partial differential equations are transformed into a system of ordinary differential equations with respect to depth by exploiting steady‐state harmonic response characteristics. Finally, the extended precise integration method is employed to obtain accurate solutions for the layered media, and numerical examples are provided to demonstrate the accuracy and applicability of the proposed approach under actual conditions.
{"title":"Viscoelastic Solution for Layered Porous Media Under Nonlinear Stokes Waves","authors":"Gan Lin Gu, Zhi Yong Ai","doi":"10.1002/nag.70230","DOIUrl":"https://doi.org/10.1002/nag.70230","url":null,"abstract":"A viscoelastic solution for layered porous media subjected to nonlinear Stokes waves is developed based on fully dynamic poroelastic theory and Stokes wave theory. Specifically, a unified expression for the wave‐induced dynamic pressure is constructed by Euler's formula in a complex exponential form, enabling the extension from linear to nonlinear wave expressions. The complex modulus of the medium is obtained by applying properties of the Gamma function to the fractional standard linear solid model. By invoking the elastic‐viscoelastic correspondence principle, the elastic solution is further extended to viscoelasticity. Then, the governing partial differential equations are transformed into a system of ordinary differential equations with respect to depth by exploiting steady‐state harmonic response characteristics. Finally, the extended precise integration method is employed to obtain accurate solutions for the layered media, and numerical examples are provided to demonstrate the accuracy and applicability of the proposed approach under actual conditions.","PeriodicalId":13786,"journal":{"name":"International Journal for Numerical and Analytical Methods in Geomechanics","volume":"14 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145920152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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